Introduction
I, like many people, don't have a super-fast internet connection. When I join a busy public world, there is a long period where most avatars haven't loaded yet. This is a source of discomfort to me. It's hard for me to interact with people if they're all just a bunch of faceless transparent blue crystals.
My suggestion
I want the most number of avatars to load as soon as possible. Therefore, I propose downloading avatars in series starting with the smallest file sizes and ending with the largest.
If the VRChat client could receive metadata about avatar file size from the server, it could sort the list of avatars to download from smallest to largest and start from the smallest. By only downloading one avatar at a time, the internet bandwidth can be dedicated to that single resource and get it loaded as fast as possible. As soon as it's downloaded, display it and start downloading the next one in the list.
I believe this method would result in the most number of avatars loading in the shortest time, leaving only a few large avatars until last.